
<h1><span class="yiyi-st" id="yiyi-12">numpy.linalg.inv</span></h1>
        <blockquote>
        <p>原文：<a href="https://docs.scipy.org/doc/numpy/reference/generated/numpy.linalg.inv.html">https://docs.scipy.org/doc/numpy/reference/generated/numpy.linalg.inv.html</a></p>
        <p>译者：<a href="https://github.com/wizardforcel">飞龙</a> <a href="http://usyiyi.cn/">UsyiyiCN</a></p>
        <p>校对：（虚位以待）</p>
        </blockquote>
    
<dl class="function">
<dt id="numpy.linalg.inv"><span class="yiyi-st" id="yiyi-13"> <code class="descclassname">numpy.linalg.</code><code class="descname">inv</code><span class="sig-paren">(</span><em>a</em><span class="sig-paren">)</span><a class="reference external" href="http://github.com/numpy/numpy/blob/v1.11.3/numpy/linalg/linalg.py#L458-L527"><span class="viewcode-link">[source]</span></a></span></dt>
<dd><p><span class="yiyi-st" id="yiyi-14">计算矩阵的（乘法）逆。</span></p>
<p><span class="yiyi-st" id="yiyi-15">Given a square matrix <em class="xref py py-obj">a</em>, return the matrix <em class="xref py py-obj">ainv</em> satisfying <code class="docutils literal"><span class="pre">dot(a,</span> <span class="pre">ainv)</span> <span class="pre">=</span> <span class="pre">dot(ainv,</span> <span class="pre">a)</span> <span class="pre">=</span> <span class="pre">eye(a.shape[0])</span></code>.</span></p>
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<tr class="field-odd field"><th class="field-name"><span class="yiyi-st" id="yiyi-16">参数：</span></th><td class="field-body"><p class="first"><span class="yiyi-st" id="yiyi-17"><strong>a</strong>：（...，M，M）array_like</span></p>
<blockquote>
<div><p><span class="yiyi-st" id="yiyi-18">矩阵要反转。</span></p>
</div></blockquote>
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<tr class="field-even field"><th class="field-name"><span class="yiyi-st" id="yiyi-19">返回：</span></th><td class="field-body"><p class="first"><span class="yiyi-st" id="yiyi-20"><strong>ainv</strong>：（...，M，M）ndarray或矩阵</span></p>
<blockquote>
<div><p><span class="yiyi-st" id="yiyi-21">（乘法）逆矩阵<em class="xref py py-obj">a</em>。</span></p>
</div></blockquote>
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</tr>
<tr class="field-odd field"><th class="field-name"><span class="yiyi-st" id="yiyi-22">上升：</span></th><td class="field-body"><p class="first"><span class="yiyi-st" id="yiyi-23"><strong>LinAlgError</strong></span></p>
<blockquote class="last">
<div><p><span class="yiyi-st" id="yiyi-24">如果<em class="xref py py-obj">a</em>不是正方形或倒置失败。</span></p>
</div></blockquote>
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</table>
<p class="rubric"><span class="yiyi-st" id="yiyi-25">笔记</span></p>
<div class="versionadded">
<p><span class="yiyi-st" id="yiyi-26"><span class="versionmodified">版本1.8.0中的新功能。</span></span></p>
</div>
<p><span class="yiyi-st" id="yiyi-27">广播规则适用，有关详细信息，请参阅<code class="xref py py-obj docutils literal"><span class="pre">numpy.linalg</span></code>文档。</span></p>
<p class="rubric"><span class="yiyi-st" id="yiyi-28">例子</span></p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">numpy.linalg</span> <span class="k">import</span> <span class="n">inv</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">a</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">array</span><span class="p">([[</span><span class="mf">1.</span><span class="p">,</span> <span class="mf">2.</span><span class="p">],</span> <span class="p">[</span><span class="mf">3.</span><span class="p">,</span> <span class="mf">4.</span><span class="p">]])</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">ainv</span> <span class="o">=</span> <span class="n">inv</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">np</span><span class="o">.</span><span class="n">allclose</span><span class="p">(</span><span class="n">np</span><span class="o">.</span><span class="n">dot</span><span class="p">(</span><span class="n">a</span><span class="p">,</span> <span class="n">ainv</span><span class="p">),</span> <span class="n">np</span><span class="o">.</span><span class="n">eye</span><span class="p">(</span><span class="mi">2</span><span class="p">))</span>
<span class="go">True</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">np</span><span class="o">.</span><span class="n">allclose</span><span class="p">(</span><span class="n">np</span><span class="o">.</span><span class="n">dot</span><span class="p">(</span><span class="n">ainv</span><span class="p">,</span> <span class="n">a</span><span class="p">),</span> <span class="n">np</span><span class="o">.</span><span class="n">eye</span><span class="p">(</span><span class="mi">2</span><span class="p">))</span>
<span class="go">True</span>
</pre></div>
</div>
<p><span class="yiyi-st" id="yiyi-29">如果a是一个矩阵对象，那么返回值也是一个矩阵：</span></p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">ainv</span> <span class="o">=</span> <span class="n">inv</span><span class="p">(</span><span class="n">np</span><span class="o">.</span><span class="n">matrix</span><span class="p">(</span><span class="n">a</span><span class="p">))</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">ainv</span>
<span class="go">matrix([[-2. ,  1. ],</span>
<span class="go">        [ 1.5, -0.5]])</span>
</pre></div>
</div>
<p><span class="yiyi-st" id="yiyi-30">可以一次计算几个矩阵的倒置：</span></p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">a</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">array</span><span class="p">([[[</span><span class="mf">1.</span><span class="p">,</span> <span class="mf">2.</span><span class="p">],</span> <span class="p">[</span><span class="mf">3.</span><span class="p">,</span> <span class="mf">4.</span><span class="p">]],</span> <span class="p">[[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">3</span><span class="p">],</span> <span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">5</span><span class="p">]]])</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">inv</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="go">array([[[-2. ,  1. ],</span>
<span class="go">        [ 1.5, -0.5]],</span>
<span class="go">       [[-5. ,  2. ],</span>
<span class="go">        [ 3. , -1. ]]])</span>
</pre></div>
</div>
</dd></dl>
